Heterozygosity for the S180L Variant of MAL/TIRAP, a Gene Expressing an Adaptor Protein in the Toll-Like Receptor Pathway, Is Associated with Lower Risk of Developing Chronic Chagas Cardiomyopathy

Background. Chagas disease is caused by the protozoan parasite Trypanosoma cruzi. Among T. cruzi-infected individuals, only a subgroup develops severe chronic Chagas cardiomyopathy (CCC); the majority remain asymptomatic. T. cruzi displays numerous ligands for the Toll-like receptors (TLRs), which are an important component of innate immunity that lead to the transcription of proinflammatory cytokines by nuclear factor-kappa B. Because proinflammatory cytokines play an important role in CCC, we hypothesized that single-nucleotide polymorphisms (SNPs) in the genes that encode proteins in the TLR pathway could explain differential susceptibility to CCC among T. cruzi-infected individuals. Methods. For 169 patients with CCC and 76 T. cruzi-infected, asymptomatic individuals, we analyzed SNPs by use of polymerase chain reaction-restriction fragment length polymorphism analysis for the genes TLR1, TLR2, TLR4, TLR5, TLR9, and MAL/TIRAP, which encodes an adaptor protein. Results. Heterozygous carriers of the MAL/TIRAP variant S180L were more prevalent in the asymptomatic group (24 [32%] of 76 subjects) than in the CCC group (21 [12%] of 169) (chi(2) = 12.6; P = .0004 [adjusted P (P(c)) = .0084]; odds ratio [OR], 0.31 [95% confidence interval {CI}, 0.16-0.60]). Subgroup analysis showed a stronger association when asymptomatic patients were compared with patients who had severe CCC (i.e., patients with left-ventricular ejection fraction <= 40%) (chi(2) = 11.3; P = .0008 [P(c) = .017]; OR, 0.22 [95% CI, 0.09-0.56]) than when asymptomatic patients were compared with patients who had mild CCC (i.e., patients with left-ventricular ejection fraction >40%) (chi(2) = 7.7; P = .005 [P(c) = .11]; OR, 0.33 [95% CI, 0.15-0.73]). Conclusion. T. cruzi-infected individuals who are heterozygous for the MAL/TIRAP S180L variant that leads to a decrease in signal transduction upon ligation of TLR2 or TLR4 to their respective ligand may have a lower risk of developing CCC.

Toll-like receptor activity in Recurrent Aphthous Ulceration

Toll-like receptors (TLR) are membrane proteins that recognize conserved molecules derived from bacterial, virus, fungal or host tissues. Activation of TLRs causes the production of cytokines that mediate inflammatory responses and drive T helper (Th) 1 and 2 cell development. As an exaggerated Th1 immune response is supposed to be involved in pathogenesis of Recurrent Aphthous Ulceration (RAU), we suggest that RAU patients may have an imbalance in TLR pathways. To study the function of TLR activation ex vivo, peripheral blood mononuclear cells (PBMCs) from RAU patients (n = 17) and controls (n = 17) were exposed to TLR2 [lipoteichoic acid (LTA), heat-killed Listeria monocytogenes (HKLM) and PamC3CSK4], TLR3 [Poly(I:C)], TLR4 [lipopolysaccharide (LPS)], TLR5 (flagellin) and TLR7 (imiquimod) ligands, and the time course of supernatant tumor necrosis factor-alpha (TNF-alpha) levels was quantified by enzyme-linked immunosorbent assay. In addition, serological and salivary TNF-alpha and soluble CD14 levels were quantified. The TNF-alpha produced by PBMCs in contact with each TLR ligand and autologous serum or saliva at the same time was also investigated. The data were analyzed by statistical multivariate tests. The control group had a higher response to LTA, whereas RAU had a higher response to HKLM. LTA and LPS interfered with the salivary stimulation of the RAU PBMC and HKLM with the stimulation of the control. Autologous serum was capable of inhibiting TLR2 responsiveness to LTA and enhancing LPS stimulation. Salivary and serological levels of sCD14 and TNF-alpha were not significantly different. Recurrent Aphthous Ulceration patients have an anomalous activity of the TLR2 pathway that probably influences the stimulation of an abnormal Th1 immune response.

Interleukin-33 attenuates sepsis by enhancing neutrophil influx to the site of infection

Sepsis is a systemic inflammatory condition following bacterial infection with a high mortality rate and limited therapeutic options(1,2). Here we show that interleukin-33 (IL-33) reduces mortality in mice with experimental sepsis from cecal ligation and puncture (CLP). IL-33-treated mice developed increased neutrophil influx into the peritoneal cavity and more efficient bacterial clearance than untreated mice. IL-33 reduced the systemic but not the local proinflammatory response, and it did not induce a T helper type 1 (T(H)1) to T(H)2 shift. The chemokine receptor CXCR2 is crucial for recruitment of neutrophils from the circulation to the site of infection(3). Activation of Toll-like receptors (TLRs) in neutrophils downregulates CXCR2 expression and impairs neutrophil migration(4). We show here that IL-33 prevents the downregulation of CXCR2 and inhibition of chemotaxis induced by the activation of TLR4 in mouse and human neutrophils. Furthermore, we show that IL-33 reverses the TLR4-induced reduction of CXCR2 expression in neutrophils via the inhibition of expression of G protein coupled receptor kinase-2 (GRK2), a serine-threonine protein kinase that induces internalization of chemokine receptors(5,6). Finally, we find that individuals who did not recover from sepsis had significantly more soluble ST2 (sST2, the decoy receptor of IL-33) than those who did recover. Together, our results indicate a previously undescribed mechanism of action of IL-33 and suggest a therapeutic potential of IL-33 in sepsis.

The essential role of toll like receptor-4 in the control of Aggregatibacter actinomycetemcomitans infection in mice

Objective: Aggregatibacter actinomycetemcomitans is an oral Gram-negative bacterium that contributes to periodontitis progression. Isolated antigens from A. actinomycetemcomitans could be activating innate immune cells through Toll-like receptors (TLRs). In this study, we evaluated the role of TLR4 in the control of A. actinomycetemcomitans infection. Material and Methods: We examined the mechanisms that modulate the outcome of A. actinomycetemcomitans-induced periodontal disease in TLR4(-/-) mice. The production of cytokines was evaluated by ELISA. The bacterial load was determined by counting the number of colony-forming units per gram of tissue. Results: The results showed that TLR4-deficient mice developed less severe periodontitis after A. actinomycetemcomitans infection, characterized by significantly lower bone loss and inflammatory cell migration to periodontal tissues. However, the absence of TLR4 facilitated the A. actinomycetemcomitans dissemination. Myeloperoxidase activity was diminished in the periodontal tissue of TLR4(-/-) mice. We observed a significant reduction in the production of tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1 beta in the periodontal tissue of TLR4(-/-) mice. Conclusion: The results of this study highlighted the role of TLR4 in controlling A. actinomycetemcomitans infection.

Colony-stimulating factor-1 suppresses responses to CpG DNA and expression of toll-like receptor 9 but enhances responses to lipopolysaccharide in murine macrophages

During bacterial infections, the balance between resolution of infection and development of sepsis is dependent upon the macrophage response to bacterial products. We show that priming of murine bone marrow-derived macrophages (BMMs) with CSF-1 differentially regulates the response to two such stimuli, LPS and immunostimulatory (CpG) DNA. CSF-1 pretreatment enhanced IL-6, IL-12, and TNF-alpha production in response to LPS but suppressed the same response to CpG DNA. CSF-1 also regulated cytokine gene expression in response to CpG DNA and LPS; CpG DNA-induced IL-12 p40, IL-12 p35, and TNF-alpha mRNAs were all suppressed by CSF-1 pretreatment. CSF-1 pretreatment enhanced LPS-induced IL-12 p40 mRNA but not TNF-alpha and IL-12 p35 mRNAs, suggesting that part of the priming effect is posttranscriptional. CSF-1 pretreatment also suppressed CpG DNA-induced nuclear translocation of NF-kappaB and phosphorylation of the mitogen-activated protein kinases p38 and extracellular signal-related kinases-1/2 in BMMs, indicating that early events in CpG DNA signaling were regulated by CSF-1. Expression of Toll-like receptor (TLR)9, which is necessary for responses to CpG DNA, was markedly suppressed by CSF-1 in both BMMs and thioglycolate-elicited peritoneal macrophages. CSF-1 also down-regulated expression of TLR1, TLR2, and TLR6, but not the LPS receptor, TLR4, or TLR5. Hence, CSF-1 may regulate host responses to pathogens through modulation of TLR expression. Furthermore, these results suggest that CSF-1 and CSF-1R antagonists may enhance the efficacy of CpG DNA in vivo.

Strategies of the African swine fever virus to manipulate innate immunity

Dissertation presented to obtain the Ph.D degree in Biology

TOLL-LIKE RECEPTORS (TLR) 2 AND 4 EXPRESSION OF KERATINOCYTES FROM PATIENTS WITH LOCALIZED AND DISSEMINATED DERMATOPHYTOSIS

There are few studies on the role of innate immune response in dermatophytosis. An investigation was conducted to define the involvement of Toll-Like Receptors (TLRs) 2 and 4 in localized (LD) and disseminated (DD) dermatophytosis due to T. rubrum. Fifteen newly diagnosed patients, eight patients with LD and seven with DD, defined by involvement of at least three body segments were used in this study. Controls comprised twenty skin samples from healthy individuals undergoing plastic surgery. TLR2 and TLR4 were quantified in skin lesions by immunohistochemistry. A reduced expression of TLR4 in the lower and upper epidermis of both LD and DD patients was found compared to controls; TLR2 expression was preserved in the upper and lower epidermis of all three groups. As TLR4 signaling induces the production of inflammatory cytokines and neutrophils recruitment, its reduced expression likely contributed to the lack of resolution of the infection and the consequent chronic nature of the dermatophytosis. As TLR2 expression acts to limit the inflammatory process and preserves the epidermal structure, its preserved expression may also contribute to the persistent infection and limited inflammation that are characteristic of dermatophytic infections.

Exploring deregulated signals involved in motor neuron-microglia cross-talk in ALS

Part of the results discussed in this thesis was presented in the following meetings: Cunha MI, Cunha C, Vaz AR, Brites D. Studying microglial-motoneuron cross-talk in ALS pathology. 6th iMed.UL Postgraduate Students Meeting, Lisbon, July 2, 2014. [Abstract and Poster] Vaz AR. Motoneuron degeneration and glial reactivity in ALS: insights from cellular to animal models. Neuroscience Seminars at IMM 2012, Instituto de Medicina Molecular, Universidade de Lisboa, Lisbon, Portugal, June 9, 2014. [Oral Communication (by invitation)]

Infección de macrófagos con el Virus Encefalitis Saint Louis: efecto sobre el fenotipo celular y la apoptosis.

El virus Encefalitis Saint Louis (VESL) (género Flavivirus) experimenta una re-emergencia en la región central del país, con la ocurrencia de un brote en Córdoba y el aislamiento de cepas de distintos genotipos. Está demostrado que los Flavivirus neurotrópicos, como VESL, replican en macrófagos y células dendríticas, tanto en el tejido local como en nódulos linfáticos satélites, para luego llegar a torrente sanguíneo y ser transportados a sistema nervioso central. Es así que el nivel de viremia inicial es regulado por la depuración del virus que realizan los macrófagos. Estas células reconocen a los virus por medio de receptores de reconocimiento de patrones moleculares asociados a patógenos, que incluyen a los receptores Toll-like (TLR). La relación entre los TLR y los virus, se fundamenta en tres aspectos: 1) los TLR al ser estimulados por moléculas derivadas de virus activan vías de señalización que inducen la producción de citoquinas pro-inflamatorias, como TNF- , IL-1, 6, 8 y 18, INF-  y , que median la respuesta inmune antiviral; 2) las señales que dependen de los TLR median efectos inmunopatogénicos, como la apoptosis y la patogénesis del virus; 3) algunas estrategias terapéuticas o profilácticas antivirales se basan en la estimulación de los TLR mediante los respectivos agonistas. Como parte de la respuesta del macrófago a la infección viral, hay proliferación, diferenciación y muerte celular. A la hora de morir, estas células pueden seguir el camino que lleva a la necrosis o el de la apoptosis. Durante la activación de la respuesta inmune frente a antígenos extraños, la apoptosis es requerida para eliminar las células efectoras, una vez que han ejecutado su función y así evitar el desarrollo de procesos deletéreos para el huésped. Estudios realizados con distintos Flavivirus documentan el incremento de apoptosis de macrófagos durante la progresión de la infección y también su relación con la severidad de la patología. De acuerdo a los antecedentes expuestos, se formulan las siguientes hipótesis de estudio: 1-El fenotipo de activación del macrófago infectado con VESL está relacionado con el genotipo viral. 2-La clase de inmunomoduladores liberados y el grado de apoptosis de los macrófagos infectados con el VESL dependen del receptor de reconocimiento utilizado por el virus.El objetivo principal es caracterizar la respuesta inmune inducida en macrófagos infectados in vitro con diferentes genotipos de VESL. Para ello se plantean los siguientes objetivos específicos: 1-Determinar la capacidad de replicación de VESL en macrófagos.2-Evaluar la expresión de molécula de superficie, receptores y la producción de inmunomoduladores en macrófagos infectados con VESL.3-Analizar el impacto de la infección con VESL sobre la apoptosis de macrófagos.4-Correlacionar la expresión de antígenos de superficie, receptores, producción de inmunomoduladores, apoptosis y carga viral con el genotipo viral que infecta al macrófago.Se utilizará una línea línea celular mieloide U937 y cepas del VESL genotipo III, V y VII. Se estudiará la infección de las mismas y determinará la expresión de: CD14, CD16, CD54/ICAM-1, HLA-DR, Fas, R-TNF, CD86, IL4R, TLR2, TLR3, TLR4 y TLR7 por Citometría de Flujo. En el sobrenadante de los cultivos infectados se cuantificarán las concentraciones de IFN-, IFN-, TNF-, IL-1, IL-6, IL-8, IL-10, IL-12, IL-18 y TGF- por técnica de ELISA.Se determinará la apoptosis en los macrófagos infectados mediante marcación con Anexina V-Ficoeritrina y análisis de fragmentación del ADN.La emergencia de esta virosis en nuestro medio amerita abordar distintos aspectos de la respuesta inmune en esta infección. El conocimiento de las características de la activación del macrófago cuando se infecta con VESL, los inmunomoduladores liberados y el impacto de la infección sobre la apoptosis de ésta célula, aportaría posibles blancos para el diseño futuro de estrategias terapéuticas o profilácticas contra esta infección.

PARTICIPACIÓN DEL RECONOCIMIENTO INMUNE INNATO EN LA RESPUESTA DE CARDIOMIOCITOS DURANTE LA INFECCIÓN EXPERIMENTAL CON TRYPANOSOMA CRUZI. Characterization of the cardiac innate immune response during Trypanosoma cruzi experimental infection.

La enfermedad de Chagas, causada por Trypanosoma cruzi, constituye la principal miocarditis infecciosa a nivel mundial. Crecientes evidencias revelan que la respuesta inmune innata tendría un rol determinante en la fisiopatología de las enfermedades cardiovasculares. La inmunidad innata es la primera línea de defensa, no específica, preprogramada para combatir agentes infecciosos. Este sistema censa la presencia de antígenos extraños a través de los receptores tipo toll (TLR) produciendo citoquinas y activando mecanismos microbicidas. Sin embargo, los TLRs también se hayan distribuidos en las células parenquimales no inmunes, jugando un importante rol tanto en la defensa como en la homeostasis de cada tejido. Durante la etapa aguda de la infección, el T. cruzi invade y se replica dentro de una amplia variedad de células y tejidos. Pero posteriormente, los parásitos son efectivamente eliminados de la mayoría de los tejidos persistiendo durante toda la vida en las células del músculo cardíaco y esquelético de los pacientes infectados. Debido a que el mantenimiento de la célula cardíaca infectada es crítica para la patogénesis de la enfermedad, los mecanismos que participan en la sobrevida de los cardiomiocitos están siendo foco de nuestro estudio. Hemos demostrado, que la infección ejerce efectos antiapoptóticos sobre células cardíacas aisladas. Nuestra hipótesis es que la inmunidad innata cardíaca estaría involucrada en el mantenimiento de la sobrevida de los miocitos así como en la defensa contra el parásito. Objetivo general: determinar la participación de la respuesta inmune innata cardíaca en el desarrollo de la enfermedad de Chagas experimental murina. Objetivos específicos: 1) Analizar el compromiso de TLRs en la respuesta anti-apoptótica y de autofagia de cardiomiocitos aislados de ratones salvajes y de ratones deficientes en TLR4, TLR2 y en MyD88, molécula adaptadora de la señalización por TLRs, sometidos a la infección con el parásito. 2) Determinar la importancia de la actividad cisteín proteasa parasitaria en el grado de infectividad y la sobrevida de cultivos primarios de ratones salvajes infectados con parásitos transgénicos que poseen disminuída o nula actividad cisteín proteasa. 3) Establecer la cinética de expresión de TLR2/TLR6, TLR4 y TLR9, factores antiapoptóticos (Bcl-2, Bcl-xL, etc.), daño cardíaco y la carga parasitaria en el tejido cardíaco de ratones infectados salvajes y/o deficientes antes mencionados. Materiales y Métodos: Los animales serán infectados i.p. con 5x103 parásitos y se determinará la cinética de expresión de los mediadores mencionados por western blot e inmunofluorescencia, la carga parasitaria será determinada por qRT-PCR. Como controles se procesarán animales inyectados con solución salina. En cultivos primarios de cardiomiocitos de ratones neonatos salvajes y deficientes infectados se estudiará la carga parasitaria, la activación de los mecanismos microbicidas (producción de óxido nítrico, metabolitos reactivos del oxígeno y del nitrógeno, ciclooxigenasa, etc.), producción de citoquinas y expresión de moléculas anti-apoptóticas (Bcl-2, Bcl-xL, Bax, etc.). Se explorará la tasa de apoptosis en cultivos deprivados de suero. La autofagia se analizará por microscopia electrónica. Cultivos controles serán mantenidos en medio o tratados con ligandos de los diferentes TLRs. Resultados preliminares sugieren que tanto TLR2 como Bcl-2 se incrementan en tejido cardíaco infectado. Esto nos lleva a profundizar en los mecanismos observados en cultivos y estudiarlos en un modelo in vivo, analizando la posible importancia que tiene la inmunidad innata cardíaca en el control del establecimiento de la infección. La comprensión de los mecanismos que mantienen la sobrevida de los cardiomiocitos y su respuesta a la infección es importante ya que el conocimiento de las bases moleculares es fundamental para el desarrollo de nuevos agentes quimioterapéuticos. Chagas disease is endemic in Central and South America and causes the most common myocarditis worldwide. We have previously reported that the cardiotrophic parasite Trypanosoma cruzi, its etiological agent, protects cardiomyocytes against apoptosis induced by growth factor deprivation activating the PI3K/Akt and MEK1/ERK signaling pathways. Recent studies have shown that local innate immunity plays a key role in initiating and coordinating homeostatic as well as defense responses in the heart. One of the mechanisms by which the innate immune system senses the presence of foreign antigens is through TLRs. The stimulation of these receptors leads to the activation and nuclear translocation of NF-kB transcription factor and the production of cytokines. Proinflammatory cytokines, in turn, appear to play a central role in the orchestration and timing of the intrinsic cardiac stress response providing, under different situations, instantaneous anti-apoptotic cytoprotective signals, which allow tissue repair and/or remodeling. The aim of the present project is to study the cardiomyocyte innate immune responses to T. cruzi infection and its role in target cell protection from apoptosis. Specific objectives: 1) Study the mechanism triggered by TLR in the anti-apoptotic response and parasite load of infected cardiomyocyte primary cultures from wild type and mice deficient in TLR2, TLR4 or MyD88. 2) Determine the effect of parasite cisteín protease activity on primary cultures from wild type mice. 3) Determine the TLR signaling-involvement in parasite load and survival indicators in deficient mice. Preliminary results showed us that cardiac-TLR2 may be involved in the anti-apoptotic effect elicited by the parasite and prompted us to establish the mechanisms triggered by the innate immunity that mediate parasite persistence within the host cell.

Interacciones inmuno-endócrinas: participación de tlr-4 y citoquinas pro-inflamatorias en la regulación de la proliferación de células lactotropas. Immuno-endocrine interactions: Contribution of tlr-4 and pro-inflammatory cytokines in the regulation of lactotroph cell proliferation.

El presente proyecto tiene como objetivo estudiar, a nivel celular y molecular, los mecanismos inmuno-endócrinos que participan en la proliferación de células lactotropas normales y tumorales frente a procesos inflamatorios inducidos experimentalmente. Una particular atención se pondrá al evaluar la contribución de IL-6 como citoquina intrahipofisaria durante el desarrollo tumoral y su rol como señal paracrina/autocrina en la senescencia hipofisaria. Debido a que agentes inflamatorios y anti-inflamatorios pueden inducir alteraciones en el crecimiento y la función hipofisaria, no se descartaría que, en el curso de una inflamación, como la inducida por el lipopolisacárido bacteriano LPS, puedan ocurrir modificaciones en el índice proliferativo de las células lactotropas y/o en la secreción de su producto hormonal, la prolactina. Dado el auge en las investigaciones referidas al campo de la modulación inmuno-endócrina, es que planteamos investigar la participación de TLR4, componente crucial del complejo proteico que inicia la señal LPS, en hipófisis normales y tumorales inducidas por estrógeno así como también en la línea celular somatolactotrópica GH3B6. Dentro de las vías de transducción de señales involucradas se determinará la participación de MAPK-ERK1/2 y de PI3K asi como la contribución de NF-kB en la regulación del crecimiento celular inducido por IL-6/LPS mediante el uso de inhibidores específicos. La microscopía electrónica y confocal, resultarán de fundamental importancia para valorar los procesos de translocación nuclear de NF-kB como así también para definir la localización ultraestructural de los mediadores mencionados. Además, se valorará el mecanismo de senescencia celular hipofisaria mediante parámetros morfológicos, bioquímicos y ultraestructurales durante el desarrollo de prolactinomas inducidos experimentalmente. Finalmente dilucidar las posibles vías de transducción de señales que se desencadenan frente a estímulos inflamatorios/proliferativos podría explicar algunos aspectos moleculares sobre la función de control del ciclo celular y las limitaciones de crecimiento en adenomas hipofisarios que subyacen en la falta de progresión de estos tumores a la malignidad. The aim of the present project is to study the immuno-endocrine mechanisms involved in the proliferation of normal and tumoral lactotrophs experimentally induced by inflammatory factors. Also, the contribution of IL-6 as a paracrine / autocrine signal in the pituitary senescence will be assessed along tumor development induced by estrogen treatment. Considering that both, inflammatory and anti-inflammatory agents can modify the pituitary function, it is possible that in the course of inflammation, as induced by bacterial lipopolysaccharide LPS, some alteration may occur in the proliferative index of lactotrophs and / or in the PRL secretion. Our main objective is to investigate the cellular and molecular mechanisms involved by the activation of TLR4, a crucial component of the protein complex initiated by LPS, in normal and pathological pituitaries induced by estrogen as well as in the GH3B6 cell line. The participation of MAPK-ERK1 / 2 and PI3K signaling pathway and the contribution of NF-kB in the proliferative responses triggered by IL-6/LPS will be analyzed by using specific inhibitors. Confocal microscopy analysis is essential to assess the process of nuclear translocation of NF-kB as well as the use of electron microscopy to define the ultrastructural localization of the above mentioned mediators. In addition, the mechanisms of pituitary cell senescence will be evaluated through morphological, biochemical and ultrastructural approaches during the development of experimental prolactinomas. Finally, the elucidation of possible signal transduction pathways which are triggered by inflammatory / proliferative stimuli, would explain some molecular aspects of cell cycle control and limitations in pituitary tumor growth that underlie the lack of progress in these pituitary tumors to malignancy.

Participación de las células supresoras mieloides (CSM) y T regulatorias (Treg) en el control de la infección con Trypanosoma cruzi y el desarrollo de la patología inflamatoria asociada a la infeccion. Role of Myeloid-Derived Suppressor Cells and regulatory T cells in the control of T. cruzi infection and the infection-associated pathology.

La infección de mamíferos con el T. cruzi resulta en diferentes alteraciones inmunológicas que permiten la persistencia crónica del parásito y destrucción inflamatoria progresiva del tejido cardiaco, nervioso y hepático. Los mecanismos responsables de la patología de la enfermedad de Chagas han sido materia de intensa investigación habiéndose propuesto que el daño producido en esta enfermedad puede ser consecuencia de la respuesta inflamatoria del individuo infectado y/o de una acción directa del parásito sobre los tejidos del hospedador. El propósito del presente proyecto es estudiar comparativamente, en dos cepas de ratones con diferente susceptibilidad a la infección y desarrollo de patología, la participación y los mecanismos efectores de las células supresoras mieloides (CSM) y las celulas T regulatorias inducidas por la infección experimental con Trypanosoma cruzi en el control de la infección con este protozoario y en el desarrollo de la patología hepática siendo los objetivos especificos desarrolar: - Investigar la generación y/o reclutamiento de células de CSM en bazo e hígado de ratones infectados con Trypanosoma cruzi y su contribución a la desigual susceptibilidad a la infección y respuesta inmune desarrollada en las cepas de ratones BALB/c y C57BL/6; - Investigar la capacidad de las CSM inducidas por la infección con T. cruzi en bazo e hígado de ratones de ambas cepas para suprimir la respuesta de células T in vitro e indagar sobre los mecanismos de supresión utilizados; - Investigar la generación y/o reclutamiento de células Treg durante la infección experimental con Trypanosoma cruzi, su participación en la desigual susceptibilidad a la infección y respuesta inmune desarrollada en ambas cepas de ratones y los mecanismos de supresión utilizados. - Analizar en tejido hepático o leucocitos infiltrantes la presencia de COX2, PGE2, MMP2 y 9, IL1b, IL6, IDO, IL10 y GM-CSF capaces de inducir la expansión de las CSM; - Dilucidar si la administración del ligando para TLR2 (Pam3CyS) previo a la infección de ratones C57BL/6 (en los cuales se detecta un menor número de CSM) es capaz de modular la respuesta inflamatoria y el daño hepático a través de la inducción de CSM y/o T reg en hígado y bazo. La comprension de los eventos celulares y moleculares que regulan la producción de citoquinas pro- y anti-inflamatorias y otros mediadores, así como el papel de los receptores de la inmunidad innata durante la infección con T. cruzi contribuirá a responder interrogantes que son claves para el diseño de nuevas estrategias de intervención inmune tendientes a preservar los mecanismos de defensa del huésped. Two nonexclusive mechanisms have been proposed to explain the Chagas’s disease pathology: 1) The pathology of the disease seems to be consequence of the inflammatory response triggered for the parasite; or 2) The damage is produced by the parasite direct effect. Recently, we reported that TLR2, TLR4 and TLR9 (innate immune response receptors) are differentially modulated in injured livers from BALB/c (lesser liver pathology) and C57BL/6 (elevated liver pathology) mice during Trypanosoma cruzi infection. The aim of our proposal is the study of role of Myeloid-Derived Suppressor Cells (MDSC) and regulatory T cells in the control of T. cruzi infection and the infection-associated pathology. Our specific aims are: -To study the induction or recruitment of MDSC in splenn and liver of BALB/c and C57BL/6 mice and their relationship with the differential susceptibility and immune response observed in these both mice strains; - To determine the ability and the mechanisms used by the T. cruzi-induced MDSC to suppress the T cell proliferative response; -To study the induction or recruitment of Treg in liver of BALB/c and C57BL/6 mice and their relationship with the differential susceptibility and immune response observed in these both mice strains; -To analize in liver tissue or tissue infiltrating lymphocytes the activation of COX2, PGE2, MMP2 y 9, IL1b, IL6, IDO, IL10 y GM-CSF known to promote the development of MDSC; -To determine whether the treatment with Pam3CyS (TLR2 ligand) is able to modulate the liver inflammatory respose and damage througth the induction of MDSC or Treg.

Uric acid is a danger signal activating NALP3 inflammasome in lung injury inflammation and fibrosis.

RATIONALE: Lung injury leads to pulmonary inflammation and fibrosis through myeloid differentiation primary response gene 88 (MyD88) and the IL-1 receptor 1 (IL-1R1) signaling pathway. The molecular mechanisms by which lung injury triggers IL-1beta production, inflammation, and fibrosis remain poorly understood. OBJECTIVES: To determine if lung injury depends on the NALP3 inflammasome and if bleomycin (BLM)-induced lung injury triggers local production of uric acid, thereby activating the NALP3 inflammasome in the lung. Methods: Inflammation upon BLM administration was evaluated in vivo in inflammasome-deficient mice. Pulmonary uric acid accumulation, inflammation, and fibrosis were analyzed in mice treated with the inhibitor of uric acid synthesis or with uricase, which degrades uric acid. MEASUREMENTS AND MAIN RESULTS: Lung injury depends on the NALP3 inflammasome, which is triggered by uric acid locally produced in the lung upon BLM-induced DNA damage and degradation. Reduction of uric acid levels using the inhibitor of uric acid synthesis allopurinol or uricase leads to a decrease in BLM-induced IL-1beta production, lung inflammation, repair, and fibrosis. Local administration of exogenous uric acid crystals recapitulates lung inflammation and repair, which depend on the NALP3 inflammasome, MyD88, and IL-1R1 pathways and Toll-like receptor (TLR)2 and TLR4 for optimal inflammation but are independent of the IL-18 receptor. CONCLUSIONS: Uric acid released from injured cells constitutes a major endogenous danger signal that activates the NALP3 inflammasome, leading to IL-1beta production. Reducing uric acid tissue levels represents a novel therapeutic approach to control IL-1beta production and chronic inflammatory lung pathology.

Contribution of TIR domain-containing adapter inducing IFN-beta-mediated IL-18 release to LPS-induced liver injury in mice.

BACKGROUND/AIMS: After treatment with heat-killed Propionibacterium acnes mice show dense hepatic granuloma formation. Such mice develop liver injury in an interleukin (IL)-18-dependent manner after challenge with a sublethal dose LPS. As previously shown, LPS-stimulated Kupffer cells secrete IL-18 depending on caspase-1 and Toll-like receptor (TLR)-4 but independently of its signal adaptor myeloid differentiation factor 88 (MyD88), suggesting importance of another signal adaptor TIR domain-containing adapter inducing IFN-beta (TRIF). Nalp3 inflammasome reportedly controls caspase-1 activation. Here we investigated the roles of MyD88 and TRIF in P. acnes-induced hepatic granuloma formation and LPS-induced caspase-1 activation for IL-18 release. METHODS: Mice were sequentially treated with P. acnes and LPS, and their serum IL-18 levels and liver injuries were determined by ELISA and ALT/AST measurement, respectively. Active caspase-1 in LPS-stimulated Kupffer cells was determined by Western blotting. RESULTS: Macrophage-ablated mice lacked P. acnes-induced hepatic granuloma formation and LPS-induced serum IL-18 elevation and liver injury. Myd88(-/-) Kupffer cells, but not Trif(-/-) cells, exhibited normal caspase-1 activation upon TLR4 engagement in vitro. Myd88(-/-) mice failed to develop hepatic granulomas after P. acnes treatment and liver injury induced by LPS challenge. In contrast, Trif(-/-) mice normally formed the hepatic granulomas, but could not release IL-18 or develop the liver injury. Nalp3(-/-) mice showed the same phenotypes of Trif(-/-) mice. CONCLUSIONS: Propionibacterium acnes treatment MyD88-dependently induced hepatic granuloma formation. Subsequent LPS TRIF-dependently activated caspase-1 via Nalp3 inflammasome and induced IL-18 release, eventually leading to the liver injury.

Bacterial flagellin elicits innate immune defenses and cardiac dysfunction in vivo

Résumé Les agents pathogènes responsables d'infection entraînent chez l'hôte deux types de réponses immunes, la première, non spécifique, dite immunité innée, la seconde, spécifique à l'agent concerné, dite immunité adaptative. L'immunité innée, qui représente la première ligne de défense contre les pathogènes, est liée à la reconnaissance par les cellules de l'hôte de structures moléculaires propres aux micro-organismes (« Pathogen-Associated Molecular Patterns », PAMPs), grâce à des récepteurs membranaires et cytoplasmiques (« Pattern Recognition Receptors », PRRs) identifiant de manière spécifique ces motifs moléculaires. Les récepteurs membranaires impliqués dans ce processus sont dénommés toll-like récepteurs, ou TLRS. Lorsqu'ils sont activés par leur ligand spécifique, ces récepteurs activent des voies de signalisation intracellulaires initiant la réponse inflammatoire non spécifique et visant à éradiquer l'agent pathogène. Les deux voies de signalisation impliquées dans ce processus sont la voie des « Mitogen-Activated Protein Kinases » (MAPKs) et celle du « Nuclear Factor kappaB » (NF-κB), dont l'activation entraîne in fine l'expression de protéines de l'inflammation dénommées cytokines, ainsi que certaines enzymes produisant divers autres médiateurs inflammatoires. Dans certaines situations, cette réponse immune peut être amplifiée de manière inadéquate, entraînant chez l'hôte une réaction inflammatoire systémique exagérée, appelée sepsis. Le sepsis peut se compliquer de dysfonctions d'organes multiples (sepsis sévère), et dans sa forme la plus grave, d'un collapsus cardiovasculaire, définissant le choc septique. La défaillance circulatoire du choc septique touche les vaisseaux sanguins d'une part, le coeur d'autre part, réalisant un tableau de «dysfonction cardiaque septique », dont on connaît mal les mécanismes pathogéniques. Les bactéries à Gram négatif peuvent déclencher de tels phénomènes, notamment en libérant de l'endotoxine, qui active les voies de l'immunité innée par son interaction avec un toll récepteur, le TLR4. Outre l'endotoxine, la plupart des bactéries à Gram négatif relâchent également dans leur environnement une protéine, la flagelline, qui est le constituant majeur du flagelle bactérien, organelle assurant la mobilité de ces micro-organismes. Des données récentes ont indiqué que la flagelline active, dans certaines cellules, les voies de l'immunité innée en se liant au récepteur TLRS. On ne connaît toutefois pas les conséquences de l'interaction flagelline-TLRS sur le développement de l'inflammation et des dysfonctions d'organes au cours du sepsis. Nous avons par conséquent élaboré le présent travail en formulant l'hypothèse que la flagelline pourrait déclencher une telle inflammation et représenter ainsi un médiateur potentiel de la dysfonction d'organes au cours du sepsis à Gram négatif, en nous intéressant plus particulièrement àl'inflammation et à la dysfonction cardiaque. Dans la première partie de ce travail, nous avons étudié les effets de la flagelline sur l'activation du NF-κB et des MAPKs, et sur l'expression de cytokines inflammatoires au niveau du myocarde in vitro (cardiomyocytes en culture) et in vivo (injection de flagelline recombinante à des souris). Nous avons observé tout d'abord que le récepteur TLRS est fortement exprimé au niveau du myocarde. Nous avons ensuite démontré que la flagelline active la voie du NF-κB et des MAP kinases (p38 et JNK), stimule la production de cytokines et de chemokines inflammatoires in vitro et in vivo, et entraîne l'activation de polynucléaires neutrophiles dans le tissu cardiaque in vivo. Finalement, au plan fonctionnel, nous avons pu montrer que la flagelline entraîne une dilatation et une réduction aiguë de la contractilité du ventricule gauche chez la souris, reproduisant les caractéristiques de la dysfonction cardiaque septique. Dans la deuxième partie, nous avons déterminé la distribution du récepteur TLRS dans les autres organes majeurs de la souris (poumon, foie, intestin et rein}, et avons caractérisé dans ces organes l'effet de la flagelline sur l'activation du NF-κB et des MAPKs, l'expression de cytokines, et l'induction de l'apoptose. Nous avons démontré que le TLRS est exprimé de façon constitutive dans ces organes, et que l'injection de flagelline y déclenche les cascades de l'immunité innée et de processus apoptotiques. Finalement, nous avons également déterminé que la flagelline entraîne une augmentation significative de multiples cytokines dans le plasma une à six heures après son injection. En résumé, nos données démontrent que la flagelline bactérienne (a) entraîne une inflammation et une dysfonction importantes du myocarde et (b) active de manière très significative les mécanismes d'immunité innée dans les principaux organes et entraîne une réponse inflammatoire systémique. Par conséquent, la flagelline peut représenter un médiateur puissant de l'inflammation et de la dysfonction d'organes, notamment du coeur, au cours du choc septique déclenché par les bactéries à Gram négatif. Summary Pathogenic microorganisms trigger two kinds of immune responses in the host. The first one is immediate and non-specific and is termed innate immunity, whereas the second one, specifically targeted at the invading agent, is termed adaptative immunity. Innate immunity, which represents the first line of defense against invading pathogens, confers the host the ability to recognize molecular structures common to many microbial pathogens, ("Pathogen-Associated Molecular Patterns", PAMPs), through cytosolic or membrane-associated receptors ("Pattern Recognition Receptors", PRRs), the latter being represented by a family of receptors termed "toll-like receptors or TLRs". Once activated by the binding of their specific ligand, these receptors activate intracellular signaling pathways, which initiate the non-specific inflammatory response aimed at eradicating the pathogens. The two pathways implicated in this process are the mitogen-activated protein kinases (MAPK) and the nuclear factor kappa B (NF-κB) signaling pathways, whose activation elicit in fine the expression of inflammatory proteins termed cytokines, as well as various enzymes producing a wealth of additional inflammatory mediators. In some circumstances, the innate immune response can become amplified and dysregulated, triggering an overwhelming systemic inflammatory response in the host, identified as sepsis. Sepsis can be associated with multiple organ dysfunction (severe sepsis), and in its most severe form, with cardiovascular collapse, defming septic shock. The cardiovascular failure associated with septic shock affects blood vessels as well as the heart, resulting in a particular form of acute heart failure termed "septic cardiac dysfunction ", whose pathogenic mechanisms remain partly undefined. Gram-negative bacteria can initiate such phenomena, notably by releasing lipopolysaccharide (LPS), which activates innate immune signaling by interacting with its specific toll receptor, the TLR4. Besides LPS, most Gram-negative bacteria also release flagellin into their environment, which is the main structural protein of the bacterial flagellum, an appendage extending from the outer bacterial membrane, responsible for the motility of the microorganism. Recent data indicated that flagellin activate immune responses upon binding to its receptor, TLRS, in various cell types. However, the role of flagellin/TLRS interaction in the development of inflammation and organ dysfunction during sepsis is not known. Therefore, we designed the present work to address the hypothesis that flagellin might trigger such inflammatory responses and thus represent a potential mediator of organ dysfunction during Gram-negative sepsis, with a particular emphasis on cardiac inflammation and contractile dysfunction. In the first part of this work, we investigated the effects of flagellin on NF-κB and MAPK activation and the generation of pro-inflammatory mediators within the heart in vitro (cultured cardiomyocytes) and in vivo (injection of recombinant flagellin into mice). We first observed that TLRS protein is strongly expressed by the myocardium. We then demonstrated that flagellin activates NF-κB and MAP kinases (p38 and JNK), upregulates the transcription of pro-inflammatory cytokines and chemokines in vitro and in vivo, and stimulates the activation of polymorphonuclear neutrophils within the heart in vivo. Finally, we demonstrated that flagellin triggers acute cardiac dilation, and a significant reduction of left ventricular contractility, mimicking characteristics of clinical septic cardiac dysfunction. In the second part, we determined the TLRS distribution in other mice major organs (lung, liver, gut and kidney) and we characterized in these organs the effects of flagellin on NF-κB and MAPK activation, on the expression of pro-inflammatory çytokines, and on the induction of apoptosis. We demonstrated that TLRS protein is constitutively expressed and that flagellin activates prototypical innate immune responses and pro-apoptotic pathways in all these organs. Finally, we also observed that flagellin induces a significant increase of multiple cytokines in the plasma from 1 to 6 hours after its intravenous administration. Altogether, these data provide evidence that bacterial flagellin (a) triggers an important inflammatory response and an acute dysfunction of the myocardium, and (b) significantly activates the mechanisms of innate immunity in most major organs and elicits a systemic inflammatory response. In consequence, flagellin may represent a potent mediator of inflammation and multiple organ failure, notably cardiac dysfunction, during Gram-negative septic shock.